Inductive heating device for metal blocks



March 31, 1964 A. FlNZl ET AL 3,127,496

r INDUCTIVE HEATING DEVICE FOR METAL BLOCKS Filed Aug. 16. 1961 2 Sheets-Sheet 1 Fig l INVENTORS.

Arno F/i'izL W [fg'ang Faber March 31, 1964 A. FlNZI ET AL INDUCTIVE HEATING DEVICE FOR METAL BLOCKS Filed Aug. 16, 1961 2 Sheets-Sheet 2 /NVENTDRS Arno FL'nzL WoLfgang Faber 55 PM JWX WWJL- United States Patent 3,127,496 INDUQTHVE A'HNG DEVICE FOR METAL BLQCKS Arno liinri, Dortmund, and Wolfgang Faber, Brambaner, Westphalia, Germany, assignors to Brown, Boverr & Cie, Alrtiengesellschaft, Mannheim, Germany, a ointstoclr corn an Fil d ag. 16, 196i, Ser. No. 131,865 Claims priority, application Germany Sept. 21, 1960 4 tllaims. (Cl. 219-1631) This invention relates to apparatus for heating metal blocks prior to working of the blocks in presses and more particularly to an improved arrangement for supplementarily heating the block heads by means of aux liary induction heating units located in the direct vicinity of the pressing equipment.

In particular, the invention provides for supplementary heating, by induction heating equipment, of the head end of a block which has already been heated uniformly throughout its entire volume at a heating station somewhat remote from the press, this supplementary heating being made to take place in the vicinity of the press just prior to delivery of the block to the press in order to promote better isothermal conditions throughout the body of the block during the working thereof in the press.

Before the further processing of metal blocks in extrusion presses or cable presses and the like, heating units, which are usually of the electric induction type, are employed to achieve a rapid and uniform heating of the metal blocks to be used. During working of the blocks in the presses, the blocks are additionally heated as a result of heat generated internally therein by work done on the metal itself in shaping it. Thus, the blocks, at the time of introducing them to the press, have a lower temperature than during the time they are being worked in the press. In order to obtain a uniform temperature of the entire block during the entire pressing operation, a procedure which is known as isothermal pressing is therefore necessary to bring the head end of the block, i.e. the part which is first shaped in the press, to a higher temperature than the remaining body portion of the block, which latter is additionally heated as a result of heat generated internally due to the working of the metal itself in the press.

In order to achieve a higher heating of the end of the block lying forward in the press, this end being referred to as the block head, it is possible to disconnect a portion of the induction coils which induce current flow in the block necessary for heating of the block so that, for example, only the block head is fully heated. It is also possible to draw the block out of the induction heating device so slowly that the back end of the block is more intensely heated than the remaining part of the block, and then to reverse the block, end for end, before inserting it in the press. Both of these methods, however, impair the optimum utilization of the heating device. Since several heating devices are often provided for use with one press, in some cases a parallel arrangement of an additional heating device is necessary to compensate for the lesser utilization of the device. In addition, especially when several parallel arranged heating devices are provided for supplying blocks to the press, these can be set up only at an appreciable distance from the press so that a correspondingly long path must be travelled by the blocks from the heating devices to the press. Thus, aside from heat lost from the block generally because of radiation, a part of the heat of the block head can flow off into the remaining part of the block, which means practically a partial, undesired, re-cooling of the block head.

In accordance with the present invention, the disadvantages of the prior known metal block heating procedures are avoided in that an inductive heating device is located in the direct vicinity of the press and the metal blocks, previously heated uniformly throughout in other heating devices located more remotely from the press, are brought by conveyor to this supplementary inductive heating device for a short time immediately before delivery thereof to the press in order that additional heating may be imparted to the block head. Since this additional heating of the block head is therefore carried out only shortly before the block is delivered to the press and moreover is performed in the immediate vicinity of the press, the heat potentials attained by the block head in the supplementary inductive heating device remain substantially unchanged until the pressing operation on the block has begun.

The supplementaiy inductive heating device can be arranged laterally at the press end of the conveyor path from the primary heating device to the press. The block head must then either be driven into the supplementary inductive heating device and after completing the supplementary heating of the block head, be driven out again or, on the other hand, the supplementary inductive heating device is driven over the block head and driven back again after the heating has been completed.

The supplementary inductive heating device can also be arranged in the direct line of the conveyor path to the press and, of course, in the direct vicinity of the press. The block then moves against a stop which fixes its position so that the block head comes to lie in the supplementary inductive heating device. After the supplementary heating of the block head has been completed, the stop is removed such as by lowering, or swinging out, or drawing back, and the block is then passed to the press. The stop, which fixes the position of the block on arrival at the supplementary inductive heating device can be provided with a limit switch which has the function of switching on the supplementary inductive heating device and, at the same time, efifects a stoppage of the conveyor. The supplementary heating of the block head can be terminated by means of a time relay which is switched on as the supplementary heating device is energized and is switched off after expiration of the time set on the relay. It is also possible to measure the temperature of the block head with a temperature measuring instrument placed in contact therewith, or with a radiation measuring instrument, and on reaching the desired value to switch off the supplementary induction heating device and initiate further guidance of the block to the point of bringing it into the press.

The foregoing as well as other objects and advantages of the invention will become more clearly understood from the following description of preferred embodiments thereof and from the accompanying drawings wherein:

FIG. 1 is a plan view illustrating one embodiment wherein the supplementary inductive heating device for the block head is arranged at the side of the main conveyor path for the uniformly heated blocks between the remotely located primary heating units and the press, the blocks being removed from the conveyor path into the supplementary inductive heating device for supplementary heating of the block heads and then returned to the conveyor for delivery to the press;

FIG. la is a plan View of the supplementary heater part of the apparatus shown in FIG. 1 but drawn to a larger scale;

FIG. 2 is also a plan view illustrating a second embodiment of the invention wherein the supplementary inductive heating device for the block head is located directly in. the conveyor path for the blocks and in the direct vicinity of the press; and

aromas FIG. 2a is a plan view of the supplementary heater part of the apparatus shown in FIG. 2 but drawn to a larger scale.

With reference now to FIG. 1, it will be seen that three primary heating units 1, 1' and 1" are arranged adjacent one another and at a point somewhat remote from the feeding-in point of the block to the press P. These primary heating units can be of the inductive type and metal blocks 2 are heated therein uniformly throughout their entire length. After reaching the desired temperature the block 2, for example, is pushed out of the heating unit 1" onto the roller conveyor path 4 which is the power driven type. Block 2 is passed along the conveyor path as far as a stop 7 which is located in the direct vicinity of the feed-in point to the press and at one side of the main conveyor path to the press. A supplementary inductive heating device 5 is located in advance of stop 7 and in the path of travel of block 2 thereto so that when the block reaches the stop, only the block head will be located within the heating device 5. In advance of the heating device 5 is a holding device 6 for the block which functions to hold the block fast against any movement during heating in the device 5. The stop device 7 is provided with a limit switch, not illustrated, actuatable, for example, by block 2 which serves to initiate the following operations; stoppage of movement of conveyor 4; actuation of holding device ti to prevent the block 2 from being hurled out of the interior of the induction heating device 5 due to the appearance of electrodynamic forces when the coil 5a of the heating device 5 is energized; and also switching on of the heating coil 5a. Together with this operational sequence, a time relay is switched on which, after the passing of a time period that is adjustable, functions to cut off energization of induction heating coil 5a. As previously explained, the switching off of a coil 5a can also be effected by means of a temperature measuring instrument after the block head has reached the desired temperature. Substantially, simultaneously with switching off of induction heating coil 5a, first the block holding device 6 is released, then over a switch device an order is given for ejection of block 2 from an ejection unit constituting a part of the overall stop device 7. Block 2 is thus pushed from the stop device 7 to a position in front of a comparatively short conveyor section 9' positioned transverse to the main conveyor 4 and there actuates a limit switch which serves to cut off this movement. By means of a further switch device, an ejection mechanism 8, located in line with conveyor section 9' and at the side of block 2 as the latter comes to rest in front of conveyor section 9', is then actuated and moves block 2 through rolling off into the press, or as shown, onto the special transverse drag 9' which conveys block 2 to a position in front of the press ram. Through a further limit switch, the switch device for the transverse motion of block 2 into the press proper is now switched off. At the same time, this limit switch actuates the switch device for returning of the transverse drag 9" which thus returns to its end position where another limit switch cuts off the conveyor mechanism of the cross drag 9'.

A somewhat different embodiment of the invention but employing the same inventive concept is illustrated in FIG. 2. Here it will be seen that the supplementary heating device 12 is arranged in front of the terminating end of conveyor 4 in the near vicinity of the press 9 by somewhat more than one length of block 2. The block 2 heated uniformly throughout its length in one of the primary induction heating devices 1, 1 or 1", leaves the latter, for example, heating device 1, and is transferred from a cross conveyor 3- onto the main conveyor 4 where it proceeds along the latter to the stop mechanism 11 so that the block head 2a projects into the supplementary heating device 12 which is located in line with conveyor 4. By means of a limit switch mounted on the stop device '11 and which is actuated on arrival of block 2, the switch device controlling conveyor 4 is cut off and a 1 block holding device 13 is actuated. This is located so as to be at the opposite end of block 2 when the head 2a of the latter is within induction heating coil 12a. The holding device 13 has the same function as holding device 6 in the embodiment of FIG. 1. At the same time, a time relay is switched on which, after expiration of an initial delay to allow the holding device to fully function, switches on the switching device for energizing coil 12a of the supplementary induction heating device 12 and also an additional time relay. After expiration of the time set on this time relay, or by use of a temperature measurement device after the block head 2a reaches the desired temperature, the time relay or the temperature measuring device, respectively functions to switch off the induction heating coil 12a. At the same time, the switch device for holder 13 is actuated so that the block 2 is freed. After this, by means of a switch device, the stop device 11 is brought out and swung away from its position in the path of block 2 on the conveyor. By means of a limit switch, or by switching off of the appropriate switch and conveyor device, this movement is ended. Next, the switch device for conveyor 4 as well as for the holder 13 is actuated so that block 2 is advanced to the stop 14 and holder 13 is swung to the side out of the way of conveyor 4 where it remains until the next block 2 is presented to the induction heating device 12. On the stop 14 is mounted a limit switch which stops conveyor 4. This limit switch, in addition, switches on the switch device for actuating the short section of conveyor 9' placed at the end of c-onveyor iand transverse thereto which then functions to take the block 2 into the press where its motion is arrested by a limit switch and it also functions to return the stop unit 11 from its swung-back position to the position shown on FIG. 2 where a part thereof extends into induction heating coil 12a ready to receive and stop the head of the next block presented to it. A further limit switch brings the stop unit 11 to :rest after it has reached the position shown in FIG. 2. The same limit switch after taking off the block switches on the device for return of conveyor 9. In the initial position, the drive for the conveyor 9' is stopped by a limit switch.

For carrying out all of the movements involved in operating the apparatus, drives of any known type can e used. Among these are hydraulic, pneumatic, electromotor and electromagnetic drives.

In conclusion, the invention is not limited to the typical embodiments which have been described and illustrated but is capable of various modifications in the construction and arrangement of components. F or example, the number of primary inductive heating units l to 1 can be greater or less than the three depicted. Moreover, the supplementary inductive heating device for the block head can be arranged so as to be displaceable, i.e. it can be pushed over the block head to be supplementarily heated and then pushed back clear of the block head when the heating has been completed. In the latter case, the control of the various movements involved can take place logically in a similar manner to what has been described in connection with the two specific embodiments which have been described.

We claim:

1. Apparatus for heating metal blocks in preparation for working in a press in accordance with the principle of isothermal pressing wherein the head end of the metal block is the first part thereof to be worked in the press which comprises a first stage heating unit for heating the blocks uniformly throughout their length and cross section, conveyor means for transporting the uniformly heated blocks from said first heating unit towards said press, a second stage heating unit of the induction type located in the immediate vicinity of said press, means for stopping the transport of said uniformly heated blocks at said second stage heating unit for a short period, the head end only of said block being further heated in said second stage heating unit, and said blocks being thereb after transported into said press along said conveyor means.

2. Apparatus as defined in claim 1 for heating metal blocks wherein a plurality of said first stage heating units are provided for heating blocks uniformly throughout, and the uniformly heated blocks are transported by said conveyor means from each of said first stage heating units to said second stage heating unit.

3. Apparatus as defined in claim 1 for heating metal blocks wherein said second stage heating unit is located along said conveyor means at a point where said uniformly heated blocks undergo a change in the direction of movement thereof, the heater coil of said second stage heating unit being arranged to receive only the head end of each uniformly heated block just prior to said change 1 in its direction of movement.

4. Apparatus as defined in claim 1 for heating metal blocks wherein said conveyor means and hence also said blocks pass through the induction heater coil of said References Cited in the file of this patent UNITED STATES PATENTS 1,800,898 Nelsen Apr. 14, 1931 2,813,959 Mitchell et al Nov. 19, 1957 2,828,398 Lombard Mar. 25, 1958 2,829,229 Metz Apr. 1, 1958 2,906,797 Guyer et a1 Sept. 22, 1959 2,995,641 Seulen et al. Aug. 8, 1961 FOREIGN PATENTS 855,987 Great Britain Dec. 14, 1960 OTHER REFERENCES Patelhold German application 1,083,555, June 15, 1960. 

1. APPARATUS FOR HEATING METAL BLOCKS IN PREPARATION FOR WORKING IN A PRESS IN ACCORDANCE WITH THE PRINCIPLE OF ISOTHERMAL PRESSING WHEREIN THE HEAD END OF THE METAL BLOCK IS THE FIRST PART THEREOF TO BE WORKED IN THE PRESS WHICH COMPRISES A FIRST STAGE HEATING UNIT FOR HEATING THE BLOCKS UNIFORMLY THROUGHOUT THEIR LENGTH AND ACROSS SECTION, CONVEYOR MEANS FOR TRANSPORTING THE UNIFORMLY HEATED BLOCKS FROM SAID FIRST HEATING UNIT TOWARDS SAID PRESS, A SECOND STAGE HEATING UNIT OF THE INDUCTION TYPE LOCATED IN THE IMMEDIATE VICINITY OF SAID PRESS, MEANS FOR STOPPING THE TRANSPORT OF SAID UNIFORMLY HEATED BLOCKS AT SAID SECOND STAGE HEATING UNIT FOR A SHORT PERIOD, THE HEAD END ONLY OF SAID BLOCK BEING FURTHER HEATED IN SAID SECOND STAGE HEATING UNIT, AND SAID BLOCKS BEING THEREAFTER TRANSPORTED INTO SAID PRESS ALONG SAID CONVEYOR MEANS. 